The Impact Of Surface Micro-dimple Array On Hydrodynamic Lubrication

Tribology is a technical discipline which is designed to save energy, protect the ecologicalenvironment and improve the quality of our lives. The applications of tribological technology aremaking a great contribution to solve the serious problems facing the world, such as the resourceshortages, the environmental disruption and so on. In recent years, the technology of surface texturehas been proven to be en effective technical means to improve the tribological properties of frictionpairs. The surface texture has caused the attention of tribology and become a hot research.Researchers have mostly been studying the tribological properties of the textured surface throughthe measurement of the friction coefficient, but less through the film thickness. The main content ofthis paper is to analysis the effects of surface texture on the tribological properties by measuring theoil film thickness under hydrodynamic lubrication.In this paper, optical interference theory was used to measure the oil film thickness. And thelubricating properties of the textured surfaces are studied under different loads and speeds. Themicro-dimples were designed from the four aspects: the diameter, the area ratio, the arrangement andthe depth. The micro-dimples were fabricated on a silicon wafer by using photolithography and wetetching process. The effects of micro-dimples on the characteristics of oil film thickness wereinvestigated through the test system of oil film. And the bearing capacity’s characteristics were got bythe establishment of the carrying capacity’s model. The mechanism that the micro-dimples improvethe lubrication performance was studied further.The results of this study showed that the micro-dimples with appropriate geometric parameters canincrease the oil film thickness, improve the carrying capacity and the performance of hydrodynamiclubrication.1. The micro-dimples with smaller diameter can effectively increase the thickness of oilfilm and improve the carrying capacity.2. The area ratio was an important factor to affect thelubricating properties of textured surface. The area ratio of5%of the micro-dimples showed optimalresults when the micro-dimples’ diameter was200μm or400μm. And when the diameter was200μm,the area ratio of5%make the carrying capacity increase obviously, which is27%higher than themaximum film’s carrying capacity of untextured surface.3. The appropriate arrangement ofmicro-dimples can improve the lubricating properties of the friction pair further. Under the same arearatio(r=5%), the arrangement of60°compared with the arrangement of0°make the maximum film’scarrying capacity increase by28%.4. The micro-dimples with shallow depth are conductive to theformation of the oil film and improve the lubricating properties of the friction pair. Summarizing the experimental laws, it was found that the mechanism of the effects ofmicro-dimples on the hydrodynamic lubrication performance may be as follows:1. The micro-dimples played a certain sealing effect and restrained the phenomenon of end vent,thereby improving the actual carrying capacity of the oil film.2. The micro-dimples can generate additional hydrodynamic pressure to improve the carryingcapacity of the oil film, and the influence of the pressure between micro-dimples would change theentire carrying capacity of friction surface.